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Incorporate ConnyOnny's iterator exercise!

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- Deciding not to have solutions in the tree right now, until I figure
  out a more general way to handle that.
- The assertions work really great as tests, actually!
- Simplifying a few of the side points-- I think they deserve their own
  exercises :)
This commit is contained in:
Carol (Nichols || Goulding)
2016-04-19 15:56:46 -04:00
parent d0f4ee1b39
commit 4bf727cbf7
4 changed files with 152 additions and 232 deletions
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164
standard_library_types/iterator1.rs
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@@ -1,164 +0,0 @@
// 1. Complete the divide function
// 2. Uncomment and complete the second part of the main function
// For part 2 there is a minor hint around line 100 and a major hint around line 128
// There are some final comments for when you are done around line 150
// Have fun :-)
// In production code you would not derive Debug, but implement it manually to get a better error message.
#[derive(Debug,PartialEq,Eq)]
enum DivisionError {
NotDivisible(NotDivisibleError),
DivideByZero,
}
#[derive(Debug,PartialEq,Eq)]
struct NotDivisibleError {
divident: i32,
divisor: i32,
}
// This function calculates a/b if a is divisible by b.
// Otherwise it returns a suitable error.
fn divide(a: i32, b: i32) -> Result<i32,DivisionError> {
}
#[allow(dead_code)]
enum OperationMode {
ListOfResults,
ResultWithList,
}
fn main() {
// These asserts check that your `divide` function works.
// In production code these would be tests
assert_eq!(divide(81,9),Ok(9));
assert_eq!(divide(81,6),Err(DivisionError::NotDivisible(NotDivisibleError{divident:81,divisor:6})));
assert_eq!(divide(81,0),Err(DivisionError::DivideByZero));
assert_eq!(divide(0,81),Ok(0));
println!("Your divide function seems to work! Good Job.");
/* Second part of main. Uncomment to continue.
// Don't change these numbers. It will break the assertions later in the code.
let numbers = vec![27,297,38502,81];
let division_results = // Do not convert the results into a Vec yet. Leave them iterable for now.
let operation_mode = OperationMode::ResultWithList;
match operation_mode {
OperationMode::ResultWithList => {
println!("{:?}", x);
assert_eq!(format!("{:?}",x), "Ok([1, 11, 1426, 3])");
},
OperationMode::ListOfResults => {
println!("{:?}", x);
assert_eq!(format!("{:?}",x), "[Ok(1), Ok(11), Ok(1426), Ok(3)]");
},
}
*/
}
// Minor hint: In each of the two cases in the match in main, you can create x with either a 'turbofish' or by hinting the type of x to the compiler. You may try both.
// Major hint: Have a look at the Iter trait and at the explanation of its collect function. Especially the part about Result is interesting.
// Final comments
// When you call the function `print_result_with_list` with x, you don't need any type annotations on x anymore.
// The compiler can infer its type through the function's input type.
#[allow(dead_code)]
// Don't use this function to solve the exercise
fn print_result_with_list(r: Result<Vec<i32>,DivisionError>) {
// side quest: why is there no semicolon in this function?
match r {
Ok(v) => println!("All numbers were successfully divided: {:?}", v),
Err(e) => match e {
DivisionError::NotDivisible(nde) => println!("Failed to divide {} by {}: Not divisible!", nde.divident, nde.divisor),
DivisionError::DivideByZero => println!("Can't divide by zero"),
},
};
}

68
standard_library_types/iterator1_solution.rs
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@@ -1,68 +0,0 @@
// In production code you would not derive Debug, but implement it manually to get a better error message.
#[derive(Debug,PartialEq,Eq)]
enum DivisionError {
NotDivisible(NotDivisibleError),
DivideByZero,
}
#[derive(Debug,PartialEq,Eq)]
struct NotDivisibleError {
divident: i32,
divisor: i32,
}
// This function calculates a/b if a is divisible by b.
// Otherwise it returns a suitable error.
fn divide(a: i32, b: i32) -> Result<i32,DivisionError> {
if b == 0 {
return Err(DivisionError::DivideByZero);
}
match a % b {
0 => Ok(a/b),
_ => Err(DivisionError::NotDivisible(NotDivisibleError{divident:a, divisor:b})),
}
}
#[allow(dead_code)]
enum OperationMode {
ListOfResults,
ResultWithList,
}
#[allow(dead_code)]
fn print_result_with_list(r: Result<Vec<i32>,DivisionError>) {
// side quest: why is there no semicolon in this function?
match r {
Ok(v) => println!("All numbers were successfully divided: {:?}", v),
Err(e) => match e {
DivisionError::NotDivisible(nde) => println!("Failed to divide {} by {}: Not divisible!", nde.divident, nde.divisor),
DivisionError::DivideByZero => println!("Can't divide by zero"),
},
};
}
fn main() {
// These asserts check that your `divide` function works.
// In production code these would be tests
assert_eq!(divide(81,9),Ok(9));
assert_eq!(divide(81,6),Err(DivisionError::NotDivisible(NotDivisibleError{divident:81,divisor:6})));
assert_eq!(divide(81,0),Err(DivisionError::DivideByZero));
println!("Your divide function seems to work! Good Job.");
// Don't change these numbers. It will break the assertions later in the code.
let numbers = vec![27,297,38502,81];
let numbers_iterator = numbers.into_iter();
let division_results = numbers_iterator.map(|n| divide(n, 27));
let operation_mode = OperationMode::ResultWithList; // you may change this
match operation_mode {
OperationMode::ResultWithList => {
let x : Result<Vec<_>,_> = division_results.collect();
//print_result_with_list(x);
assert_eq!(format!("{:?}",x), "Ok([1, 11, 1426, 3])");
},
OperationMode::ListOfResults => {
let x : Vec<_> = division_results.collect();
println!("{:?}", x);
assert_eq!(format!("{:?}",x), "[Ok(1), Ok(11), Ok(1426), Ok(3)]");
},
}
}

144
standard_library_types/iterator3.rs Normal file
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// This is a bigger exercise than most of the others! You can do it!
// Here is your mission, should you choose to accept it:
// 1. Complete the divide function to get the first four tests to pass
// 2. Uncomment the last two tests and get them to pass by filling in
// values for `x` using `division_results`.
// Scroll down for a minor hint for part 2, and scroll down further for
// a major hint.
// Have fun :-)
#[derive(Debug, PartialEq, Eq)]
pub enum DivisionError {
NotDivisible(NotDivisibleError),
DivideByZero,
}
#[derive(Debug, PartialEq, Eq)]
pub struct NotDivisibleError {
dividend: i32,
divisor: i32,
}
// This function should calculate `a` divided by `b` if `a` is
// evenly divisible by b.
// Otherwise, it should return a suitable error.
pub fn divide(a: i32, b: i32) -> Result<i32, DivisionError> {
}
#[cfg(test)]
mod tests {
use super::*;
// Tests that verify your `divide` function implementation
#[test]
fn test_success() {
assert_eq!(divide(81, 9), Ok(9));
}
#[test]
fn test_not_divisible() {
assert_eq!(
divide(81, 6),
Err(DivisionError::NotDivisible(NotDivisibleError{
dividend: 81,
divisor: 6
}))
);
}
#[test]
fn test_divide_by_0() {
assert_eq!(divide(81, 0), Err(DivisionError::DivideByZero));
}
#[test]
fn test_divide_0_by_something() {
assert_eq!(divide(0, 81), Ok(0));
}
// Iterator exercises using your `divide` function
/*
#[test]
fn result_with_list() {
let numbers = vec![27, 297, 38502, 81];
let division_results = numbers.into_iter().map(|n| divide(n, 27));
let x //... Fill in here!
assert_eq!(format!("{:?}", x), "Ok([1, 11, 1426, 3])");
}
#[test]
fn list_of_results() {
let numbers = vec![27, 297, 38502, 81];
let division_results = numbers.into_iter().map(|n| divide(n, 27));
let x //... Fill in here!
assert_eq!(format!("{:?}", x), "[Ok(1), Ok(11), Ok(1426), Ok(3)]");
}
*/
}
// Minor hint: In each of the two cases in the match in main, you can create x with either a 'turbofish' or by hinting the type of x to the compiler. You may try both.
// Major hint: Have a look at the Iter trait and at the explanation of its collect function. Especially the part about Result is interesting.